Bamboo open web joist

ABSTRACT

Bamboo open web joists are disclosed herein. One aspect of the invention is directed toward an open web joist design comprising a plurality of structural components made from compressed bamboo segments. Some of the structural components are formed into arched shapes. The structural components are built into a built-up beam comprising end members and span members comprising a frame, with a plurality of arched components positioned within the frame. Several fastener plates comprising a sheet with integral spikes are pressed into the structural components to hold the members together. The arched members define an open space in the built-up joist, through which mechanical components, electrical components, ducting, and other materials can pass.

TECHNICAL FIELD

Embodiments of the present invention relate to open web joists for structural members made of a fibrous material, such as bamboo.

BACKGROUND

Wood is a familiar structural material because its properties are well known and it has been used to construct buildings for many years. Despite its long history of use, the material is limited in many respects. Wood is relatively expensive to grow because it requires large plots of land and heavy machinery to harvest. Trees mature very slowly and are unable to produce the highest quality lumber until they reach an advanced age. Today's demand for construction materials has made it very difficult to produce high-quality lumber efficiently because of the economic pressure to produce lumber quickly, before it has a chance to reach its full mature strength. Also, there is much debate about the environmental impact caused by extensive foresting.

There are structural limitations to wood as a building material as well. Structural members used to span a distance, such as joists, are commonly constructed out of wood. The material, however, limits the size and layout of buildings that can be constructed with wooden joists without added supports. A wooden joist with traditional dimensions of approximately nine inches in height is limited in length to between sixteen and twenty feet. Another drawback of conventional I joist designs is that they do not permit ducting, electrical and mechanical equipment, and other components to easily pass through the joists. A conventional solution is to route ducting elsewhere such as through walls, or through other passages added to the flooring or ceiling. This solution compromises valuable interior space. Another approach is to cut holes or channels in the joists, but doing so is also undesirable because any cut in the wood significantly weakens the member. To offset the weakening caused by the cuts, the joists are built larger and larger. However, even increasing the size of the overall joist in many cases does not distribute the weakness of a local cut over the span of the joist. Larger joists also compromise interior space, are more expensive, and are heavier. Using more material to make larger beams also accelerates the environmental impact of wood harvesting. Accordingly, there is a need for a material that overcomes these drawbacks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an edge view of a structural component made from bamboo fibers for use with a built-up structural member.

FIG. 1B is an end view of a structural component made from bamboo fibers for use with a built-up structural member.

FIG. 2 is an illustration of a plurality of shapes into which a structural component can be formed.

FIG. 3 is an illustration of a built-up structural member.

FIG. 4 contains charts of test data.

DETAILED DESCRIPTION

Aspects of the present invention are directed generally toward structural members composed of fibrous material, such as bamboo. One aspect of the invention is directed toward a bamboo joist comprising a pair of end members, a first and second span member extending between the pair of end members. The end members and the span members define a frame. A plurality of shaped members are positioned in the frame. The arched members have a first leg, a second leg, and an integral arched or angular portion supporting between the first and second legs. The first and second legs of the arched members are positioned against the first span member, and the arch portion is immediately adjacent to the second span member. A plurality of fasteners, such as fastener plates that have a plurality of spikes extending from a plate portion, securely connect the arched members to the span members and/or the end members of the frame. For example, fastener plates securely fix the first and second legs one of the span members and a fastener plate securely fixes the arch portion to the other span member. Fastener plates are also used to securely fix the span and end members of the frame together.

Other aspects of the invention are directed toward a built-up structural beam, comprising a plurality of continuous, shaped members, such as curved members that each having a first end, a second end, a convex side, and a concave side. A lower span member extends substantially the length of the structural beam, and the plurality of the curved or angular members are positioned with the concave side facing the lower span member. The first and second ends are securely fixed to the lower span member, such as via fastener plates. An upper span member extends substantially the length of the structural beam, and the convex side of the curved members is securely fixed to the upper span member. A first end member and a second end member are securely fixed to the upper and lower span members and to at least one of the plurality of curved members. The curved members, the upper and lower span members, and the end member are formed of bonded bamboo segments.

Related aspects of the invention are directed toward a method of forming an open-web bamboo joist. The method includes forming a plurality of bamboo components comprising bamboo span components, bamboo end components, and curved bamboo components, and forming a rectangular frame by connecting the bamboo span components to the bamboo end components. The method continues by placing the curved bamboo components in the frame such that a convex side of the curved bamboo components faces toward one of the bamboo span components, ends of the curved bamboo components abutting at least one of another curved bamboo component or a bamboo end component. The method also includes fastening the bamboo span components, the bamboo end components, and the curved bamboo components together by pressing a fastener plate having spikes into the bamboo components.

Other aspects of the invention are directed toward a structural member made of a bamboo building material that include bamboo segments manufactured by laminating or strand processes, such at the processes described in U.S. Pat. No. 7,147,745 and/or U.S. Pat. No. 5,543,197, both of which are incorporated herein in their entirety.

Various embodiments of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these embodiments. One skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or functions may not be shown or described in detail, so as to avoid unnecessarily obscuring the relevant description of the various embodiments.

The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section.

References throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment and included in at least one embodiment of the present invention. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

FIGS. 1-3 illustrate various features of an open web joist in accordance with various embodiments of the invention. FIGS. 1A and 1B are depictions of a component 110 of a structural member. FIG. 1A shows an end 112 of the component 110, and FIG. 1B shows an edge 114 of the component 110. The component 110 is constructed of segments 118, which are joined together to form the component 110. The resulting structural component 110 can then be cut or machined to desired dimensions.

One method of joining the segments 118 together comprises drying and glue-coating a plurality of layers 120, 122, and 124. Outer nodes, husk, and inner membrane material (not shown) originally found on the bamboo is removed before applying the glue. Substantially many types of bamboo can be used. The longitudinal axes of the segments 118 in each layer are generally parallel to one another, each layer having segments oriented in substantially different directions with respect to the next adjacent layers thereto. For example, the segments 118 in layers 120 and 124 extend along the component 110, and layer 122 extends out of the plane of FIG. 1A. The layers 120, 122 and 124 of segments 118 are compressed and bonded together until the glue cures into a single integral structure. Another method of constructing component 110 involves laminating bamboo strands in random stacked parallel strips (not shown), then fusing the strips together with adhesives under pressure. Using either of these methods, a structural component 110 can be constructed, from which a larger structural member can be built.

FIG. 2 illustrates shapes 130 and 132 into which the component 110 of FIGS. 1A and 1B can be formed according to various embodiments. In some embodiments, once the component 110 is formed it can be placed into a mold and pressed with heat, moisture and/or pressure to bend, twist, or otherwise shape the component 110 until the component 110 permanently takes the desired shape 130 or 132. Shape 130 is an arch shape with a generally uniform radius or curvature throughout the shape 130. Shape 132 is an alternative design in which the component 110 is formed into three generally straight portions 134, between which are two curved, elbow sections 136. It is to be appreciated that these shapes 130 and 132 are some examples of shapes that structural component 110 can take, but the present disclosure is not limited to these shapes. The structural component 110 can take virtually any shape.

FIG. 3 illustrates an embodiment of an open web structural member 140 built from a plurality of structural components 110. In this embodiment, the structural member 140 is built into a joist. It is to be appreciated that other structures for other uses can be built using these disclosed techniques and components. The embodiments described herein are for illustration and not limitation. In an embodiment, the structural member 140 comprises end members 142 and upper and lower span members 144 and 146. The end members 142 and the span members 144 and 146 are constructed to form a rectangular frame. Arched (e.g., curved or angular) members 148 are placed in the frame between the upper and lower span members 144 and 146. In this embodiment, the arch members 148 are shaped with a generally uniform radius of curvature, and the arch member 148 extends from the lower span member 146, contacts the upper span member 144, and extends back down to contact the lower span member 146. A plurality of arched members 148 can be placed with adjacent arch members 148 abutting one another. While FIG. 3 shows three arch members 148 in the frame, it is understood that more or fewer arch members 148 can be placed in the frame for a structural member 140 of a different length or in another embodiment. The resilient nature of the bamboo fibers and the shape of the arch members 148 contribute to the strength and rigidity of the structural member 140. Each arched member 148 acts like a leaf spring. Because of the constraints of the frame, the curved members 148 help the structural member 140 to withstand compressive and/or tensile forces from all directions. Each arch member 148 is fixed to and held in place by a pair of end members 142, a pair of adjacent arch members 148, or by an end member 142 on one side and an arch member 148 on the other.

At locations where two structural components meet, a fastener plate 150 can be placed on a face 152 of the structural member 140. In an embodiment the fastener plate 150 can comprise a metal sheet with a plurality of spikes protruding from the sheet. The spikes can be pressed into the bamboo material of the structural member 140 to hold the components together. The spikes can be angled in any direction to better resist strain in a certain direction. The spikes can be formed integrally with the sheet, or can be nails or staples or the equivalent that pierce the sheet and the structural component 140. In some embodiments, the fastener plate 150 is also glued to the structural components 140. The fastener plates 150 can be generally rectangular as shown in FIG. 3; in other embodiments the fastener plates 150 can have other shapes. In general, the more surface area the fastener plate 150 has in contact with the structural member 140, the stronger the bond between the fastener plate 150 and the structural member 140. The configuration of components in structural member 140 provides for a larger surface area than current joist design for the fastener plate between structural components (e.g., between the end members 142, the upper and lower span members 144 and 146, and the arched members 148).

The arched member 148 can have the shape 130 or 132 shown in FIG. 2, or any other suitable shape. The nature of bamboo constructed according to this disclosure provides greater strength and larger modulus of elasticity than traditional solid wood joists and other wooden beams. When structural member 140 comprises a joist, the joist can span significantly longer distances than traditional wooden joists. (e.g., from between 40 and 60 feet, rather than 16 to 20 feet reached by traditional, wooden joists using the same profile.) In addition to greater strength, the arched member 148 provides an open space 160 through which mechanical components, electrical wiring, ducting, or any other equipment can pass. The structural member 140 can be used, for example, as a joist to support a ceiling and/or floor of a building. The open space 160 permits the ceiling and/or floor to be substantially as thin as the joist because the ducting, the wires, and other elements can pass through, there is no need for additional thickness to the ceiling to account for these elements. The structural member 140 is also stronger than conventional joists because no holes have been cut in the member 140 to allow the ducting to pass through.

FIG. 3 illustrates a built-up structural member 140 with three arched members 148. In other embodiments, the structural member 140 can have more or fewer arched members 148, including incomplete arched members 148. For example, in some embodiments an arched member near the end member 142 (or at another location) can be a half (or other fraction) of the arched member 148 comprising approximately 90 degrees of a circle (as opposed to 180 degrees, as depicted in FIG. 3). In one embodiment, the end members 142 can be widely sized in anticipation that the beam will be cut to fit a given installation on or during construction, such that the beam can be shortened some distance without interfering with and still supporting the arched members 148.

FIG. 4 contains several data charts 150 including strength values of bamboo structures configured according to an embodiment. The values shown in the charts 150 are intended to show qualitatively the advantages made possible by bamboo structural members arranged and configured according to the present disclosure. The present disclosure, however, is not limited to configurations in which these numbers are achieved. The charts 150 illustrate the performance of bamboo structures as compared to conventional lumber members using various fastener and loading schemes.

The above-detailed embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise form disclosed above. Specific embodiments of, and examples for, the invention are described above for illustrative purposes, but those skilled in the relevant art will recognize that various equivalent modifications are possible within the scope of the invention. For example, whereas steps are presented in a given order, alternative embodiments may perform steps in a different order. The various aspects of embodiments described herein can be combined and/or eliminated to provide further embodiments. Although advantages associated with certain embodiments of the invention have been described in the context of those embodiments, other embodiments may also exhibit such advantages. Additionally, not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, i.e., in a sense of “including, but not limited to.” Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Use of the word “or” in reference to a list of items is intended to cover a) any of the items in the list, b) all of the items in the list, and c) any combination of the items in the list.

In general, the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification unless the above-detailed description explicitly defines such terms. In addition, the inventors contemplate various aspects of the invention in any number of claim forms. Accordingly, the inventors reserve the right to add claims after filing the application to pursue such additional claim forms for other aspects of the invention. 

1. A bamboo joist, comprising: a pair of end members; a first span member and a second span member extending between the pair of end members, wherein the end members and the span members define a frame; a plurality of arched members positioned in the frame, individual arched members having a first leg, a second leg, and an arch portion between the first and second leg, wherein the first and second legs of the arched members are positioned against the first span member, and the arch portion of the arched members contacts the second span member; and a plurality of fastener plates, individual fastener plates comprising a plate and a plurality of spikes extending from the plate, wherein the spikes are pressed into the members at corners of the frame where the arched members contact the span members, and where the arched members contact the end members, the fastener plates being configured to fasten the arched members in the frame.
 2. The bamboo joist of claim 1 wherein the end members, the span members, and the arched members are formed by: forming a plurality of layers comprising dried and glue-coated bamboo segments; stacking the plurality of layers with adjacent layers being positioned with bamboo fibers extending in different directions; and compressing and bonding the layers together until the layers form a single integral structure.
 3. The bamboo joist of claim 1 wherein the end members, the span members, and the arched members are formed by: forming laminated bamboo strands; placing the strands in a random stacked parallel strips; and fusing the strips together using pressure and adhesives between the strips.
 4. The bamboo joist of claim 1 wherein the arch portion, the first leg, and the second legs of the arched members comprise an arch of substantially uniform radius.
 5. The bamboo joist of claim 1 wherein the first and second legs are generally straight.
 6. The bamboo joist of claim 1 wherein the spikes are integrally formed with the fastener plate.
 7. The bamboo joist of claim 1 wherein the frame comprises a front side and a back side, and wherein the fastening plates are positioned on at least one of the front side and the back side.
 8. The bamboo joist of claim 1 wherein the arched members are formed by placing a bamboo structural component in a mold and applying at least one of heat, pressure, and moisture to the bamboo structural component in the mold.
 9. The bamboo joist of claim 1 wherein the arch portion comprises a generally straight middle portion that is configured to contact the second span member.
 10. A built-up structural beam, comprising: a plurality of curved members, each having a first end, a second end, a convex side, and a concave side; a lower member extending substantially the length of the structural beam, the plurality of curved members being positioned with the concave side facing the lower member and the first and second ends contacting the lower member; an upper member extending substantially the length of the structural beam, the convex side of the curved members contacting the upper member; a first end member and a second end member positioned adjacent to the upper and lower members and adjacent to one of the plurality of curved members; and a plurality of fastener plates comprising a sheet of material with a plurality of spikes extending from the sheet, wherein the spikes are pressed into the built-up structural beam to fasten members together; wherein the curved members, the upper and lower members, and the end member are formed of bonded bamboo segments.
 11. The built-up structural beam of claim 10 wherein the curved members are semi-circular sections with substantially uniform radius of curvature.
 12. The built-up structural beam of claim 10 wherein the curved members, the upper and lower members, and the end members are formed by: drying bamboo segments; coating the bamboo segments with glue; arranging the segments into layers with bamboo fibers extending in a uniform direction; stacking the layers such that bamboo fibers in consecutive layers extend in substantially different directions; compressing the layers together into an integral structure.
 13. The built-up structural beam of claim 12 wherein the bamboo segments in the layers are randomly arranged.
 14. The built-up structural beam of claim 10 wherein the curved members comprise a first straight section, a first elbow, a second straight section, a second elbow, and a third straight section, wherein the second straight section is configured to contact the upper member and to extend substantially parallel to the upper member.
 15. The built-up structural beam of claim 14 wherein the first and second elbows comprise a bend of less than 90 degrees in the curved member.
 16. The built-up structural beam of claim 10 wherein the end members are configured to be trimmed to fit without interfering with the curved members.
 17. A method of forming an open-web bamboo joist, comprising: forming a plurality of bamboo components comprising bamboo span components, bamboo end components, and curved bamboo components; forming a rectangular frame by connecting the bamboo span components to the bamboo end components; placing the curved bamboo components in the frame such that a convex side of the curved bamboo components faces toward one of the bamboo span components, ends of the curved bamboo components abutting at least one of another curved bamboo component or a bamboo end component; and fastening the bamboo span components, the bamboo end components, and the curved bamboo components together by pressing a fastener plate having spikes into the bamboo components.
 18. The method of claim 17 wherein forming the plurality of bamboo components comprises: cutting bamboo into bamboo segments; drying the bamboo segments; coating the segments with glue; placing the segments into layers with bamboo fibers extending substantially in a uniform direction throughout the layer; stacking the layers; compressing the layers together into a solid structure.
 19. The method of claim 18 wherein the bamboo components comprise three or more layers of bamboo segments.
 20. The method of claim 17, further comprising: removing husk, outer nodes, and inner membrane from the bamboo; and arranging the layers such that each successive layer contains bamboo fibers aligned in a direction different than a previous layer.
 21. The method of claim 17 wherein forming the curved bamboo component comprises placing a straight bamboo component in a mold with a shape and applying at least one of heat, pressure, and moisture to the straight bamboo component until the straight bamboo component takes the shape of the mold and the glue is cured.
 22. The method of claim 21 wherein the shape includes a first elongated portion, a first elbow, a second elongated portion, a second elbow, and a third elongated portion. 